1. Field of the Invention
The present invention relates to Curvularia verruculosa haloperoxidases and isolated nucleic acid fragments comprising nucleic acid sequences encoding the haloperoxidases. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the nucleic acid sequences as well as methods for producing the haloperoxidases. The invention further relates to methods of use of the haloperoxidases.
2. Description of the Related Art
Haloperoxidases catalyze the oxidation of a halide ion (X=Cl.sup.-, Br.sup.-, or I.sup.-) in the presence of hydrogen peroxide (H.sub.2 O.sub.2) to the corresponding hypohalous acid (HOX): EQU H.sub.2 O.sub.2 +X.sup.- +H.sup.+ .fwdarw.H.sub.2 O+HOX
If an appropriate nucleophilic acceptor compound is present, the hypohalous acid will react with the compound to form a halogenated compound. Haloperoxidases can also catalyze peroxidase reactions on certain substrates in the absence of halide ions, but the substrate spectrum is broadened in the presence of halide ions due to unspecific reactions of the substrate and the hypohalide ion.
Haloperoxidases are widespread in nature being produced by mammals, plants, algae, lichen, bacteria, and fungi. Haloperoxidases are probably the enzymes responsible for the formation of naturally occurring halogenated compounds. There are three types of haloperoxidases, classified according to their specificity for halide ions: Chloroperoxidases (E.C. 1.11.1.10) which catalyze the chlorination, bromination and iodination of compounds; bromoperoxidases which show specificity for bromide and iodide ions; and iodoperoxidases (E.C. 1.11.1.8) which solely catalyze the oxidation of iodide ions.
The first discovered haloperoxidases were determined to contain heme as a prosthetic group or co-factor. However, more recently, it has become apparent that there are numerous non-heme haloperoxidases as well. Bacterial haloperoxidases have been found with no prosthetic group. In addition, a number of other non-heme haloperoxidases have been shown to possess a vanadium prosthetic group. Haloperoxidases containing a vanadium prosthetic group are known to include seaweed bromoperoxidases, and at least one type of fungal chloroperoxidase from Curvularia inaequalis (van Schijndel et al., 1993, Biochimica Biophysica Acta 1161:249-256; Simons et al., 1995, European Journal of Biochemistry 229: 566-574; WO 95/27046).
Haloperoxidases, like other oxidoreductases, are of current interest because of their broad range of potential industrial uses. For example, haloperoxidases have been proposed for use as an anti-microbial agent.
It is an object of the present invention to provide new haloperoxidases which can be produced in commercially useful quantities.